Cerebral stroke is an important disorder, which ranks fourth in Japanese mortality and ranks first in the causes of being bedridden, and is a disease caused due to cerebral ischemia. It can be said that treatment in the acute phase is important for cerebral ischemic diseases including cerebral stroke to improve the prognosis. A leading therapeutic method which has presently attracted the attention is a thrombolytic agent including a plasminogen activator (hereinafter, described as “tPA”); however, the use thereof is limited to within 4.5 hours and only a dozen or so percent of patients can benefit from the effects thereof (see Non Patent Literature 1). Part of the reason is that a blood-brain barrier becomes weak over time after cerebral ischemia and that the risk of hemorrhagic cerebral stroke increases due to the use of a thrombolytic agent such as tPA.
In recent years, the inventors have found for the first time that prothymosin α is a substance having a protective action on nerve cell death and cerebral apoplectic diseases can be alleviated by this inhibitory effect on nerve cell death (see Patent Literature 1). The inventors have also found that prothymosin α has an inhibitory effect on cerebral stroke and ischemic glaucoma in mice and rats (see Non Patent Literatures 2 to 4). The inventors have further found that prothymosin α has an action to protect a blood-brain barrier from a weakening in the blood-brain barrier, and have revealed an active body comprising 30 amino acids in rat prothymosin α and 9 amino acids in the sequence, which are important for the expression of its activity (see Patent Literature 2).